Originally Published: 08 FEB 23 01:21 ET

Updated: 08 FEB 23 12:51 ET

By Nouran Salahieh and Holly Yan, CNN

(CNN) -- The flames may have died down, but a cloud of anxiety now wafts through East Palestine, Ohio.

It's been five days since a train carrying the toxic chemical vinyl chloride derailed in the village of 5,000 people near the Pennsylvania border.

The wreckage burned for days, threatening a widespread, deadly explosion before crews Monday managed controlled detonations to release the chemical that can kill quickly at high levels and hike cancer risk.

Workers used small charges to blow a tiny hole in each rail car carrying vinyl chloride. The hazardous substance spilled into a trench, where it was burned away.

But it's still too early to say whether it's safe for evacuated residents to return.

Water samples in the area are still being analyzed, officials said Tuesday afternoon.

Three miles from the derailment site, Linda Murphy is using bottled water for her family until they feel sure their well water is safe.

"That's what we bathe in, that's what we drink, that's what we cook with, and that's what I also give to my animals," Murphy told CNN affiliate WEWS.

"So it's a major concern. And they could not reassure me the water was safe to drink. They didn't say it wasn't and absolutely refrained from saying that it was."

In addition to water testing, "air monitoring continues until we can verify that the area is safe and it's gonna stay safe to allow people to return," James Justice of the Environmental Protection Agency said Tuesday.

National Guard members were set to collect samples at homes and businesses within the evacuation zone, Ohio National Guard Maj. Gen. John Harris said Tuesday.

"They will sample areas where in the low spaces where any effective material may have settled," Harris said. "They'll be going into various residences and various businesses, sampling in basements, sampling surfaces."

The EPA had warned that residents even tens of miles away would smell odors coming from the site since the byproducts of the controlled burn can be smelled "at levels much lower than what is considered hazardous."

Some people have noticed "odors and smoke," and teams were sent to collect air quality readings at those locations, Justice said. "We didn't find any levels of concern at that time."

East Palestine's fire chief said he won't let anyone return until he feels it's safe for his family to do so.

"Once the Ohio Department of Health, the United States Environmental Protection Agency in conjunction with the East Palestine Fire Department and Norfolk Southern Railroad have determined that this is safe for East Palestine residents to return to their homes -- and, quite frankly, once I feel safe for my family to return -- we will lift that evacuation order and start returning people home," Fire Chief Keith Drabick said Tuesday.

What vinyl chloride could do to humans .

The train that derailed had more than 100 cars. About 20 of them were carrying hazardous materials, and 10 of those derailed, the National Transportation Safety Board said.

Five of those train cars contained vinyl chloride -- a man-made substance used to make PVC that burns easily at room temperature.

Vinyl chloride can cause dizziness, sleepiness and headaches. It has also been linked to an increased risk of cancer in the liver, brain, lungs and blood.

Breathing high levels of vinyl chloride can make someone pass out or even die if they don't get fresh air, the Ohio Department of Health said.

As of Tuesday, four of those five cars had been cleared from the wreckage, and crews were working to remove the fifth car, Norfolk Southern official Scott Deutsch said.

"They'll be inspected by the NTSB. Once that's complete, you'll see us cutting those cars up and removing them from the site," Deutsch added.

Residents sue Norfolk Southern

A local couple and a business owner filed a lawsuit Tuesday against Norfolk Southern Railroad, accusing the company of negligence.

The suit, filed in the US District Court of Northern Ohio, accuses the company of failing to maintain its tracks and equipment as well as failing to reasonably warn the general public.

The suit seeks unspecified compensatory and punitive damages, as well as legal fees.

"We are unable to comment on litigation," a Norfolk Southern spokesperson said Wednesday.

The cause of the derailment remains under investigation, the NTSB said.

The train crew got an alert about a mechanical issue before the derailment and investigators found video showing "preliminary indications of mechanical issues" on one of thr railcar's axles, NTSB Member Michael Graham has said.

Investigators have asked for records from Norfolk Southern and are looking into when the possible defect happened as well as the response from the train's crew -- which included an engineer, conductor and conductor trainee, Graham said.