The Birmingham Water Works now says it is investigating a large number of damaged and discolored trees in the area surrounding its Shades Mountain Filter Plant, and said it is “seriously looking into this matter” to determine whether the damage was caused by an accidental release of chlorine gas last month.

On Feb. 27, 55 people were sent to local hospitals after chlorine gas was released from the plant. U.S. Highway 280 closed in both directions for approximately two hours, and some nearby residents were told to remain in their homes for several hours until an all-clear was given. The Water Works said the release occurred after sodium hypochlorite and ferric sulfate were accidentally mixed at the plant.

In the weeks since the accident, a large number of pine trees around the plant began showing signs of discoloration, including in a residential neighborhood and church in Mountain Brook. The Valley Christian Church, located next to the plant, has 62 pine trees on its property that all appear to have brown and dying needles, according to a volunteer who tends the grounds at the church.

Birmingham Water Works spokesman Rick Jackson previously told AL.com that the utility was not responsible for discolored or damaged vegetation near the filter plant, but on Thursday said he had been referring to a different situation and that he did not know the extent of the damage to trees that has been observed around the plant when he made those comments.

“A concern of our customers is a concern of ours,” BWW Interim General Manager Michael Johnson said in a news release. “We want to continue being good stewards of the community. So, we’re taking every step to bring attention and rectification to this situation as we possibly can.”