Maine State Police said a South Portland man died Thursday from a medical problem while at work in Dayton.

Stephen McCausland, spokesman for the state police, identified the man as Craig Libby, 61.

Libby collapsed Thursday afternoon while working at the gravel pit on Goodwin Mills Road owned by Dayton Sand and Gravel Co., police said.

“The death is likely from natural causes and not from any injuries while on the job,” McCausland said in a statement issued Thursday night.

Goodwin Mills Fire Chief Roger Hooper said Libby was climbing down a ladder attached to a bucket truck when he went into cardiac arrest and fell. Hooper’s department sent an ambulance to the work site around 2:48 p.m. but was unable to resuscitate Libby.

The death is the second at the business in two years. Shawn Hutchins, 41, died in December 2012 after falling about 80 feet from a manlift at Dayton Sand and Gravel.