ICHMOND, Ind. Fire investigators have ruled the cause of the massive Richmond warehouse fire as undetermined.The April 2023 fire at a plastic warehouse burned for a week and forced thousands to evacuate.Indiana State Fire Marshal Steve Jones shared the findings with WRTV Investigates Kara Kenney. The fire is undetermined, said Jones. To do the fire investigation right, weve got to see all the right things to be able to demonstrate this is how the fire started. Weve got to have something that would ignite a fuel. If we cant find it, see it, document it, its always going to be undetermined.Fire rulings are classified in four categories according to the National Fire Protection Association: Accidental: Fires that are not the result of a deliberate human act  Natural: Fires caused by natural events like lightning, earthquakes, or wind  Incendiary (Intentional): Fires that are deliberately set when the person knows it's not allowed  Undetermined: Fires where the cause cannot be provenJones said the Indiana State Fire Marshal, ATF and Richmond Fire Department spent hundreds and hundreds of manhours to try to determine what caused the fire, however, they were not able to. Jones said one factor is fire investigators were not able to get up close for a week because it took firefighters so long to put out the massive fire. It delayed our ability to get in and observe things, said Jones. We could have if the fire was put out in a day. We might have been able to see something, but the fire went on for quite a while. The amount of water dumped on the scene also made it difficult to figure out what caused the fire, Jones said. When the warehouse plastics caught fire, it sent plumes of black, toxic smoke billowed into the air. Residents expressed concern about their health. RELATED | EPA begins cleanup at Richmond warehouse fire site Jones acknowledged many residents want to know what caused the fire. We absolutely want to determine the cause of the fire, said Jones. It helps prevent other fires if we know whats causing the fires. We put a lot of time into this. WATCH | Drone video of massive Richmond fire DRONE VIDEO | Richmond Industrial FireIts common for fire investigators to rule a fire as undetermined. According to the National Fire Protection Association, in 2022, there were 36 large-loss fires or explosions in the United States. In 42 percent, investigators found a cause, but 58 percent of the fires were undetermined, unknown or not reported. The Indiana State Fire Marshal said they were able to determine where the massive Richmond fire started. We have an area of 20 X 20 outside of the building by a semi-trailer that is the origin of the fire, said Jones. But to know what actually ignited the fire, we dont have anything tell us what that was. The State Fire Marshal was not able to tell WRTV on which parcel of land the fire started. The agency declined to provide WRTV a copy of the fire investigation report. Those are protected reports, said Jones. We do not release our investigation reports. The fire broke out a plastic recycling facility, partly owned by Cornerstone Trading Group. The City of Richmond took ownership of another portion in 2021. RELATED | City of Richmond cited property owner in 2019 for fire hazardsThe city and Cornerstone Trading Group have been pointing fingers at each other as to who was responsible. A class action lawsuit filed by two Richmond residents alleges the fire broke out on the citys portion of the property. Pictures show combustible plastic scraps and waste materials both inside and outside the warehouse. The class action lawsuit alleges the city and Cornerstone were aware of the fire hazards and did not take adequate steps to address them. WRTV Investigates has reached out to the City of Richmond and Cornerstone Trading Group for comment on the ruling of undetermined. Longtime Richmond resident John Frye said the ruling is not sitting well with him."I think they're hiding something," said Frye. "There's something they're not telling us. Something is up and I'd like to know what it is."Frye had to evacuate his home as a result of the fire.He said he reported kids playing at the site in the years leading up to the fire."I think somebody set it on fire," said Frye. In 2019, the City of Richmond conducted an inspection and found: Excessive plastic materials stored in and around the buildings constituting a fire hazard Substantial amounts of materials strewn about the properties such that combustible materials are located with 10 feet of a lot line Insufficient means of ingress and egress due to materials stored in and near the premises, as well as combustible material being stored near exits and in enclosures for stairways or ramps Insufficient fire suppression Insufficient illumination of means of egress Loose material blowing around the unsafe premises Roof damage allowing water to infiltrate, leaning walls, decaying foundation, and masonry falling outThe citys Unsafe Building Commission issued an order requiring the owner to remediate the properties.Included in the citys order to the property: Repair roofs, walls and structural components to comply with city code and state laws; or remove structures Remove materials to bring means of egress in compliance with city code and state law Install fire suppression and fire alarms to comply with city code and state law Remove materials to comply with city code and state law Building needs to comply with all emergency lighting Repair and activate all fire suppression and fire alarms