Fire officials have determined that the cause of a four alarm fire that ripped through an inn located at 13 South Boulevard on Thursday was accidental in nature.

An investigation by the Onset Fire Department, Wareham Police Department, and State Fire Marshal's Office found that the blaze started by soldering plumbing pipes, according to Onset Fire Captain Howard Andersen.

The fire originated in the first floor bathroom after plumbing work was done in the earlier that the day, he said.

The fire broke out just before 11:30 p.m. More than 90 firefighters from the Onset, Wareham, Bourne, Carver, Marion, Mattapoisett, Middleborough, and Plymouth fire departments responded to the scene. The state Fire Marshal and Plymouth County Sheriff's Department also responded.

Onset firefighters declared the fire extinguished at roughly 3:30 a.m., but remained on the scene until Friday afternoon monitoring the site.

There were no injuries reported, according to the Onset Fire Department.

The property owner is in the process of boarding up the inn, according to Town Administrator Mark Andrews, who was on the scene Friday afternoon.

The inn is owned by Antonio Gomes, who is currently living in Florida, said his son, Joe, who was at there Thursday.

Joe was nearly speechless as he watched the fire consume the building.

"Thanks to the fire departments," Joe said. "We really appreciate everything [the fire and police departments] did."

The inn was undergoing renovations and was unoccupied. It was slated to become a sober house for affluent recovering addicts, catering to doctors, lawyers, and other wealthy former drug and alcohol users who had been through treatment and were seeking a safe, stable environment to begin a sober life.

Renters John Coughlin and his father Steven Coughlin had begun renovating the building earlier this year with plans for Hopewell Recovery to manage the property. Hopewell Recovery operates several sober-living houses in Massachusetts and Florida.

The proposed sober home was met with much opposition from Onset residents who worried about how the home would affect the neighborhood.

In a statement released Friday Brian Kenney, of Hopewell Recovery, stated: "We are deeply saddened by the fire and loss that occurred late Thursday evening at the South Blvd. property. We are however all very grateful that no one was injured and that the emergency response teams were able to control and extinguish the fire. While the property is rebuilt and returned to it's original condition our goal will be to make the best of sad situation and use this as an opportunity to dispel rumors that have been circulating in the community and work to build relationships with elected officials and members of the community. It is our sincere desire, and always has been, to be a good neighbor and friend to those in our community."

John Coughlin and Steven Coughlin could not be reached for further comment.

Reporter Cyndi Murray contributed to this report.