Local police chiefs worry public safety in the Merrimack Valley could be imperiled as Methuen begins the process of laying off more than half its police force over a contract dispute.

“It’s absolutely a public safety emergency because you can’t run a police department of a city our size with half our force,” said Methuen police Chief Joseph Solomon.

Pink slips began going out to 50 Methuen officers on Thursday. Solomon said the drastic reduction to his force would leave just enough officers to work patrols, and is worried Methuen would have to rely on aid from neighboring departments, state police or the Northeastern Massachusetts Law Enforcement Council.

Lawrence police Chief Roy Vasque expects his department to shoulder some of the burden, both in manpower and money spent paying his officers to work overtime covering Methuen’s calls.

“It’s definitely a concern,” Vasque said. “If we don’t have the bodies, it’s definitely going to put a strain on us.”

Layoff notices were being handed out to officers as they arrived for the 4 p.m. shift change Thursday afternoon and will continue throughout the weekend, said Paul Fahey, chief of staff to Methuen Mayor James Jajuga. Officers are entitled to a hearing under civil service laws before they are officially laid off. Officers will continue to work their normal shifts until the hearings, tentatively scheduled for Feb. 6, Fahey said.

Methuen, a city of about 50,000 residents on the New Hampshire border, has 95 police officers: 71 patrolmen, 23 superior officers and the chief.

The cuts to the patrolmen come as the city is embroiled in a contract dispute involving the pay of ranking officers.

The superior officers’ current contract included raises that could have seen each of the department’s five captains earning $434,841 on average, city officials said. A compromise agreement reached last July would have lowered those salaries to about $188,206 on average per captain, officials said.

City councilors felt those raises were still too high and refused to fund the agreement during budget deliberations last summer and as recently as Tuesday.

Jajuga moved ahead with paying ranking officers at the rates set forth in the compromise anyway. The city is now on track to run out of money to pay the police department at its current staffing levels by March, necessitating the layoffs so as not to illegally overspend its budget, city officials said.

Methuen is already under state financial oversight for overspending its school budget in fiscal 2018.

A spokesman for the Executive Office of Public Safety and Security said state police would evaluate any request for assistance from Methuen.