Officials have not yet determined what sparked a boat fire at Jackson’s Marina in Hampton Bays shortly before 10 p.m. on Friday.Southampton Town Police Sergeant James Cavanagh said this week that while its cause is still being investigated, the blaze was contained to a single boat, a 41-foot commercial fishing vessel owned by Russell Brisson of Middle Island. The boat sustained significant damage, authorities said.No injuries were reported, and volunteers with the Hampton Bays Fire Department put out the flames.The Riverhead Town fire marshal’s office is leading the investigation since representatives of that department were the first to arrive on the scene Friday night, according to Southampton Town’s Chief Fire Marshal Cheryl Kraft. She explained that the two towns often share resources as part of an emergency preparedness agreement.As of Tuesday afternoon, the Riverhead fire marshal’s office had not yet determined a cause.The alarm came in at 9:53 p.m. Friday and, within minutes, police and firefighters converged at the Shinnecock Bay marina.