Authorities say a man climbed to the top of a blast furnace and refused to come down, prompting evacuation of an arts and entertainment venue at the Pennsylvania site.
Venue operator ArtsQuest tweeted Saturday that the "emergency situation" that began Friday night was still going on, hours later.
The SteelStacks campus remained closed.
An outdoor concert had been scheduled but about 1,500 people were evacuated after the man climbed up the furnace shortly before 7 p.m. Friday and perched several hundred feet above the venue.
Police released a photo and asked the public's help in identifying the man, who balanced precariously on a single steel beam at Bethlehem Steel Corp..
Police officers climbed to a platform below the man and were talking to him.