The number of completed foreclosures last year in Massachusetts dropped by nearly 13 percent to 7,424, down from 8,531 the previous year, the Warren Group said in a press release.

But the number of foreclosure petitions started in the Bay State increased by more than 35 percent to 17,152. In 2011, there was a big drop in petitions as lenders slowed the process as their procedures came under scrutiny, said the Warren group, a Boston firm that tracks real estate activity..