CHICAGO (WBBM)  -- The federal government plans to investigate an incident that forced a Delta Airlines flight to return to Midway Airport yesterday after taking off for Atlanta.

WBBM's Bernie Tafoya reports.

The Federal Aviation Administration says a back cargo door came off Delta Flight 4718 shortly after taking off from Midway Airport.  FAA spokeswoman Elizabeth Cory says the plane was about 60 miles southwest of Chicago when the pilot reported a pressurization problem and headed back to Midway. 

She says none of the 63 passengers was injured.

Cory calls the incident "very serious" and says investigators are "going to be looking at maintenance (of the plane), rules of flight what happened and why".

Cory says when the cargo door came off, then a couple of pieces of luggage flew out of the plane.  Neither the luggage nor the door have been found yet.

Delta Director of Corporate Communication, Maria Schnabel said previously that the crew detected that one of two back bin doors had been improperly closed and two bags had fallen out.

After inspection, Delta decided to cancel the flight in order to get the back door fixed. All passengers were re-assigned to another flight, Schnabel said.