British police are investigating a series of “unexplained” deaths Monday after three men were apparently struck by a train in south London ahead of the morning rush hour.

The bodies of the men – believed to be in their 20s – were found alongside spray paint cans near the Loughborough Junction station around 7:30 a.m. local time, according to Sky News.

"At this time, we are treating their death as unexplained as we make a number of immediate inquiries,” said British Transport Police Detective Superintendent Gary Richardson. “I would ask anyone who was near to Loughborough Junction this morning, and saw something which they think might be relevant, please contact us as soon as possible."

Transport police said the three were hit by a train, according to the Associated Press – but the circumstances surrounding their deaths were not immediately clear.

Investigators combing the scene for evidence were spotted taking pictures of graffiti, Sky News reported.

"As far as I understand it, if they've been caught in that section of track when a train came through then they really wouldn't have had much options" police superintendent Matthew Allingham was quoted as saying.

London Mayor Sadiq Khan, on Twitter, said his office was in "close contact with the British Transport Police who are urgently investigating this incident.

"My heart goes out to the families of the three people killed at Loughborough Junction station this morning,” he added.

Train traffic in the area had been delayed as police were on scene to investigate.