Protection One Inc., a Lawrence-based security monitoring company, said Tuesday that its second-quarter loss widened because of higher amortization and interest expenses.

For the three months ended June 30, the company reported a loss of $8.1 million, or 32 cents a share, compared with a loss of $6.7 million, or 36 cents a share, in the year-ago period.

Revenue increased 39 percent to $93.1 million from $67.2 million, a gain attributed largely to results of the April acquisition of Integrated Alarm Services Group Inc., which was completed.

Protection One, which has 72 employees in the I-70 Business Center in North Lawrence, reported a $2.4 million merger-related severance cost, as well as $17 million in amortization and depreciation expenses, up from $10.4 million in the second quarter of 2006.

Protection One shares fell 27 cents, or 2 percent, to close Tuesday at $12.85 on Nasdaq.

Also Tuesday, Protection One said that Eric A. Devin had become vice president for finance. Replacing him as principal accounting officer is Sarah Strahm, a certified public accountant who spent nine years at PricewaterhouseCoopers LLP.