CHARLOTTE (AP) — A North Carolina police officer was killed early Wednesday as she and fellow officers were investigating a traffic accident on Interstate 85, officials said.

According to a news release from Charlotte-Mecklenburg police, officers responded to a call in the southbound lanes of I-85 on the east side of the city after a tractor-trailer spilled a load of grain onto the highway.

Shortly after 3:30 a.m., another tractor-trailer heading south collided with a truck cab, causing them to hit multiple CMPD cars, the news release said. The department said Officer Mia Goodwin, 33, was pronounced dead at the scene from injuries she received in that crash. Three other officers were taken to a Charlotte hospital, where they were treated and released, CMPD said.

CMPD Chief Johnny Jennings told a news conference that Goodwin, who joined the department in October 2015, was married to a Charlotte firefighter. They had three children, and Goodwin had just returned from maternity leave, Jennings said.

An investigation into the accident is continuing, the department said.