A fire at the Owl Metals recycling facility that caused the Peninsula Expressway to shut down last weekend has rekindled, prompting an air quality alert.

“The crews are actively extinguishing the current fire,” Baltimore County Fire Department spokesperson Travis Francis said. “We know that deep-seated fire takes days to extinguish and often do rekindle.”

The Maryland Department of the Environment is advising sensitive groups to limit their outdoor activities near the recycling facility due to air quality samples taken Thursday near the scene of the fire, the fire department said.

“When combined with weather conditions that could concentrate pollution, [the samples] show that sensitive groups in that area should avoid outdoor activities and everyone in that area should limit strenuous activities,” the department said Thursday afternoon.

Francis said the cause of the rekindling is unknown but that it could be combustibles still burning below the debris. The weather can also affect it, he said.

“The fire rekindled this morning, which is pretty common for a fire with the intensity of the size of the fire this weekend,” Francis said.

“The fire is under control. There is no threat of spreading.”

Fire personnel first responded to a three-alarm fire at the Owl Metals Inc. recycling center at 1936 Rettman Lane in Dundalk on Saturday.

Because several portions of the building had collapsed, firefighters were attempting to subdue the blaze from outside, Baltimore County Fire Department Capt. Len Stewart said Saturday.

“It’s a large warehouse,” Stewart said, “and because the recyclables are stacked up, hotspots keep breaking out.”

No injuries were reported, though one man was taken to a local hospital as a precautionary measure after inhaling some smoke.

The Peninsula Expressway reopened Sunday.

Baltimore Sun reporters Mary Carole McCauley and Matt Hubbard contributed to this article.

Have a news tip? Contact Glynis Kazanjian at gkazanjian@baltsun.com or 301-674-7135.