By MARK SCOLFOROHARRISBURG, Pa. (AP) â¿¿ Calls to Pennsylvania's unemployment compensation service centers have mysteriously skyrocketed since September, and the agency doesn't know why. The volume of calls to the centers rose to nearly 8 million in September, compared with slightly more than 900,000 a year earlier, Labor and Industry Secretary Julia Hearthway told state lawmakers in a letter Monday. In October the calls exceeded 11 million, and then reached 15.5 million in November. The problem is all the more perplexing because the unemployment claim caseload is on the decline, measured either by number of initial claims or by the duration of claims, Hearthway wrote in the letter, obtained Tuesday by The Associated Press. "We are looking at all possibilities that may explain this dramatic increase," Hearthway wrote. She promised to use "all appropriate and available resources to uncover the causes of this aberration." State legislators have been fielding complaints from constituents, said Erik Arneson, spokesman for the Senate Republican caucus. He welcomed Hearthway's letter, saying eligible claimants deserve to have their paperwork processed without an undue burden. On Tuesday, the ranking Democrat on the House Labor and Industry Committee wrote to colleagues to say he would reintroduce a bill that would direct state funds to shore up unemployment compensation service centers. House Democrats held a public hearing two months ago about busy signals and long wait times in the phone system. "When a person loses their job and reaches out to a service center for help, the very least they expect is for somebody to pick up the phone and talk to them," said Bill Patton, House Democratic spokesman. "For hundreds of thousands of Pennsylvanians without jobs, that is not happening." Labor and Industry Department press secretary Sara Goulet said the state has been working with Verizon to figure out what has happened. Among the possible causes are automated calls. In the past month some numbers linked to high volumes of incoming calls have been blocked, and that seems to have helped, she said.