The location of the power surge, which was attributed to National Grid's network, was somewhere north of Boston. National Grid spokeswoman Debbie Drew said there was "a line outage on a transmission line in the Wakefield/Lynn/Melrose area" at about the same time a problem was reported on the commuter rail system.
"It is not entirely clear what occurred (Monday) morning; we are looking into the details and what may have caused this event," Drew said. "We are investigating the event, but have not yet identified the cause"
National Grid officials are investigating whether power generation stations in the area or animal contact or debris on the line could have caused the problem.
"National Grid gave no explanation where the surge emanated from and what caused the surge, " said Scott Farmelant, a spokesman for the Massachusetts Bay Commuter Railroad Co., which runs the commuter rail service for the T.
The surge and subsequent signal problems caused delays on a total of 19 trains between 6 a.m. and 11 a.m. on the Newburyport/Rockport line, including eight trains that make stops in Hamilton-Wenham.
The lengthiest delay was from the inbound train that normally leaves Hamilton-Wenham at 7:19 a.m. – it arrived in Boston 24 minutes late. The inbound train that usually leaves Hamilton-Wenham at 9:55 a.m. was 20 minutes late and the outbound train that typically departs Hamilton-Wenham at 8:54 a.m. was also 20 minutes late.
Delays for the other trains headed north and south from Hamilton-Wenham ranged from eight to 16 minutes.
Farmelant said trains were back on schedule by 11:23 a.m.
In all, delays north of Boston on Monday morning ranged from eight minutes to as long as 26 minutes, Farmelant said. Six of the delayed trains were late by less than 10 minutes.
Train signals, while virtually imperceptible to the casual rider, form the backbone to the commuter rail system. A power surge can fry a signal, Farmelant said.
"We are in communication with the MBCR about this event and will share our findings with them," said Drew, the National Grid spokeswoman.