Two off-duty Philadelphia firefighters died this weekend, possibly from heart attacks, Fire Commissioner Lloyd Ayers said today.

Robert Underwood, 47, collapsed at home Saturday and was taken to Nazereth Hospital in Northeast Philadelphia, where he was later pronounced dead, Ayers said.

Mitch McClain, 40, was serving with Air Force Reserves at McGuire Air Force Base in New Jersey when he also died on Saturday, Ayers said.

"We're just supporting the families and helping where we can," Ayers said.

Underwood, who was married with two children, joined the Fire Department in 1985 and was assigned to Ladder Company 28 at Cottman Avenue and Loretto Street.

McClain, who was married with one child, joined the department in 2002 and was assigned to Ladder Company 25 at Ridge and Midvale Avenues.

Contact staff writer Robert Moran at 215-854-5983 or bmoran@phillynews.com.