Researchers at Colorado State University identified much higher levels of benzene and other toxins in the air near a well blowout site north of Fort Collins than initially reported.

According to CBS Colorado, the smell of chemicals remained powerful more than a month after a Chevron well shot oil, gas, and water into the air near Galeton for several days.

Researchers found levels of benzene, a potent carcinogen, that were two to three times greater than those reported to residents by the Colorado Department of Public Health and Environment.

The blowout led to the evacuation of 14 homes, 10 of which still remaining unoccupied due to continued cleanup efforts, Chevron told the news outlet.