Will be updated. This is a developing story.
Updated 1:46 p.m.
Lambert Airport has tweeted that all passengers are off the plane:
Learjet landed at 1:30pm without incident.Passengers have been deplaned.#flystl
— Lambert-STL Airport (@flystl) March 4, 2013
Updated 1:33 p.m.
The plane has emergency landed at Lambert Airport, apparently without incident.
The plane is registered to a Texas-based company, Aerometro LLC and originated from Wooster, Ohio.
After earlier reports stated that the plane was going to try to make an emergency landing at Downtown St. Louis Airport in Cahokia, Ill., new reports state that the plane will now try to make an emergency landing at Lambert St. Louis International Airport.
Based upon all that we know about the plane thusfar (make, model, pattern of circling and intended airport), we can say that we believe this is the plane in question.
An official at a southern Illinois airport says an inbound Learjet with eight people aboard has landing gear trouble and is preparing for an emergency landing.
Diane Earhart of St. Louis Downtown Airport in Cahokia said Monday afternoon that air traffic control has confirmed the aircraft's landing gear is not functioning correctly. She says the pilot is circling the airport to determine when and how to land.
Fire trucks, ambulances and emergency crews can be seen on the airport tarmac (See livestream of video here).
St. Clair County Emergency Management Agency's 911 Director Herb Simmons says they have fire and emergency responders at the Cahokia airport on standby. He says responders are waiting to see if the flight lands in Cahokia or goes to St. Louis, Mo.
Cahokia is 5 miles south of St. Louis.