BANGOR, Maine — Bangor Housing Authority officials may never know what caused contamination that may have led some Autumn Park West residents to take ill, according to the authority’s executive director.

Last week, tenants in four one-bedroom units at the complex on Union Street were evacuated after air quality tests revealed “significantly elevated” levels of ethanol and some other chemicals, including isopropanol, isobutane and acetone, according to a report from Brewer-based TP Environmental Consulting.

The report goes on to state that those chemicals are “commonly found at clandestine methamphetamine laboratory sites” or places where pharmaceuticals are abused. It provides details of the effects of methamphetamine exposure, its symptoms and how it affects air quality.

The findings, which Bangor Housing received on March 12 — two days after testing — prompted the evacuation. The test results also sparked a police investigation at one apartment, and a thorough cleanup. Two residents are still staying in hotel rooms paid for by the housing authority.

Residents, including Laurie Baker, started to notice “God-awful,” difficult-to-describe odors in February, shortly after a new resident moved into the apartment below hers, Baker said Monday.

Some reported it smelled like burning rubber or plastic, while others picked up a “dirty” smoky smell. Every time someone from the housing authority visited in response to complaints, they didn’t smell anything unusual, according to housing authority Executive Director Mike Myatt.

Baker said she recently began to notice health symptoms. She woke up with skin irritation that resembled sunburn on her face, neck, arms, legs and feet. Her dog, Bella, has been suffering from respiratory problems for the past month, Baker said. Baker has gone to her doctor for two blood tests since she started showing odd symptoms and is waiting for results, she said.

Police and Bangor firefighters were invited into the apartment below Baker’s on separate occasions after complaints from neighbors, and didn’t turn up evidence of illegal drug activity either time, according to Bangor Housing Authority and police officials.

Police searched the apartment in question for more than two hours on March 13, according to Myatt. Neither police, nor officials from the housing authority air-quality testing group have been able to determine exactly what caused the high chemical levels.

“There’s no illegal activity going on,” Myatt said.

As of Monday, the only explanation management has is that there was “bad air” in the building.

“I wish we could have found something,” Myatt said of the search for what caused the high chemical levels.

Since it hasn’t been able to determine a source, the housing authority brought in a professional cleaning crew to thoroughly clean and air out four apartments in hopes of eliminating the smell and removing the contamination. The resident of the apartment police searched has since moved out, according to Baker.

On Monday morning, management began a second round of air-quality testing in the apartments to ensure that the rooms are safe before allowing residents to move back, possibly in the middle of this week.

“We’re hoping that it’s resolved quickly and that we can get these people back in their homes,” Myatt said.