Light, powdery snow about a week and a half ago is continuing to play havoc with PATCO service, and the problem may continue for the near future.

The type of snow that fell Jan. 7 was of a consistency easily sucked up into trains' traction motors, officials from the Delaware River Port Authority said Wednesday. If the direct current motors have even microscopic flaws in the waterproof copper coating over coils, the moisture can eventually short out the engines, said John Rink, PATCO's general manager. Since the storm, PATCO has had to repair 21 traction motors, at a cost of up to $18,000 each.

Each car has a traction motor on each axle —four per car — and a six-car train requires 20 of its 24 traction motors functioning to operate.

PATCO moves about 40,000 riders a day between New Jersey and Philadelphia.

PATCO riders have been suffering from cancellations and delays up to a half-hour since the storm. Trains have stopped mid-trip to strand passengers at stations, and just Tuesday, the problem caused four trains to be pulled from service. Two other trains were canceled due to unrelated problems. The situation has been exacerbated because PATCO can use only 96 of the 120 cars in its fleet, officials said. The shortage is largely due to an ongoing rehabilitation project.

Riders have also complained about a lack of information on delays, and on how to find alternative modes of travel, such as New Jersey Transit buses.

"The thing is communication," said Larry Davis, who maintains the watchdog Twitter account @PatcoWatchers, "being able to get timely, correct information to people."

PATCO officials issued an apology Wednesday and at the monthly board meeting said they were working on improving the accuracy of information on boards at stations and through smartphone apps.

About a third of PATCO's cars have been upgraded by Alstom Transport of Hornell, N.Y., as part of a $194 million project that began putting refitted cars on the rails in May 2015. Improvements include a sensor system that can detect when moisture may be affecting a traction motor, giving workers advance notice and a chance to resolve the problem before a short occurs. As a result, the rehabbed cars have been much less affected by the moisture problem, officials said. The full fleet won't be upgraded until 2018.

Officials said they believed enough time had passed since the storm that the problems were largely resolved, but wouldn't say they were over.

"You would expect you're not going to see the same level of problems," said John Hanson, chief executive for the DRPA, which oversees PATCO.

Protecting a DC motor from powdery snow is difficult, officials said, because enclosing the engine would create other problems with the heat it generates. A more permanent solution would be to replace the motors with an alternating current system, which has a different design that wouldn't be affected by moisture the same way. The cost to convert all of PATCO's cars, though, would be about $100 million.

The troubles this week aren't new. Snow-related engine failures happened in January 2014, and PATCO isn't the only transit agency affected. More than 200 cars on SEPTA's Regional Rail fleet have DC motors, and about a dozen have had to be repaired because of snow,  spokesman Andrew Busch said. Market-Frankford Line subway cars use an AC motor and aren't susceptible, he said. Regional Rail schedules have not been significantly affected by damage to the cars, though, Busch said.