UPS grounds its fleet of MD-11's, sources say

UPS has grounded its fleet of McDonnell Douglas MD-11's, the type of plane involved in Tuesday’s deadly crash in Louisville, Kentucky, two sources familiar with the situation told NBC News Friday.

UPS did not immediately respond to a request for comment.

A photo seen by NBC news showed a screen in a plane that directed pilots to return and which read: “Per UPS MD11 are not to depart effective immediately."

At least 14 people have died in the crash, officials said. The UPS flight, headed from Louisville to Honolulu, crashed around 5:15 p.m. as it was taking off and struck an industrial area near the airport, causing a huge fire and killing the three crew in the plane and others on the ground.

A UPS MD-11 cargo plane sits idle on the tarmac on Wednesday at Muhammad Ali International Airport in Louisville, Ky.Michael Swensen / Getty Images

Video shows that the left engine of the plane caught fire during takeoff and immediately detached, National Transportation Safety Board member Todd Inman said Wednesday.

The NTSB is the lead agency in the investigation.

On Friday night, Mayor Craig Greenberg said that the remains of a 14th victim had been found at the crash site.

"We pray for each of the victims' families, and pray that no additional victims were lost as our first responders continue to search and seek answers," Greenberg said in a video.

UPS is the largest employer in the Louisville metro area, with around 25,000 workers. The airport where the disaster happened, Louisville Muhammad Ali International Airport, is a main hub for the company's global air network.