MBTA officials hope to have a clear answer in roughly two weeks about what caused a June 11 Red Line derailment as they await final test results from an outside laboratory.

T officials said on Monday that engineers have reviewed preliminary results of a metallurgical analysis undertaken to determine what caused a breakdown on the 50-year-old train car or its five-year-old wheel truck, but that they want to receive responses to several key questions before reaching a conclusion.

Deputy General Manager Jeff Gonnveille said he expects that work to wrap up in about two weeks. “Once that is done, we will be at a point where we can identify clearly what we believe the root cause of this incident is,” he said.

Investigators had previously ruled out problems with the track, operator error, and foul play as possible causes.

As the train derailed just outside the JFK/UMass stop, it damaged two buildings housing signal infrastructure and destroyed a third, essentially knocking out the automated signal system. Since then, crews have had to signal trains manually when it is safe to proceed, a process that has slowed rail travel.

Some electronic signals have been restored, but sections of the system between JFK/UMass and both North Quincy and Fields Corner are still using employees to direct trains by hand. Gonneville said repair work should be completed in October.

“At this point we feel confident that we should be fully restored by October but there is a strong possibility that we will be able to do better than that,” Gonneville said, adding that the p.m. rush hour delays are a secondary effect of the derailment. Because the Red Line has “very little operational flexibility,” other incidents such as medical emergencies, police actions or disabled vehicles — which have happened frequently in recent days — are more likely to cause delays.

Trips from Braintree to South Station are still delayed by 10 to 15 minutes, Gonneville said, compared to 25- to 30-minute delays soon after the derailment.

While the MBTA is once again running close to a full fleet of Red Line trains during the morning rush hour, it has had about four fewer trains per hour on the tracks in the evening in recent weeks.