NTSB Investigators conduct Unmanned Aircraft System operations for the Norfolk Southern freight train derailment near East Palestine, Ohio.
CNN  — 

A toxic train wreck in Ohio ignited a dayslong inferno, spewed poisonous fumes into the air, killed thousands of fish and left residents wondering if it’s safe to live in East Palestine.

The fiery derailment in early February prompted fears of a catastrophic explosion of vinyl chloride – a highly flammable chemical linked to an increased risk of cancer. After a mandatory evacuation order, crews released vinyl chloride into a trench and burned it off – averting an explosion but spawning new health concerns.

Officials have said tests show the air and municipal water are safe and allowed residents to return home. But some have reported a variety of new health problems including rashes, nausea, bloody noses and trouble breathing.

Train operator Norfolk Southern must handle and pay for all necessary cleanup, and the company has sent some hazardous waste out of state – fueling more questions about safety.

CNN is chronicling the latest events as new information unfolds. Here’s what we know:

Correction: An earlier version of this story misspelled the first name of Ohio Environmental Protection Agency official Tiffani Kavalec.