LONDON — A fire aboard an empty 787 at Heathrow Airport spooked Boeing investors Friday, as they feared the reemergence of battery problems that grounded the plane for months earlier this year.
Boeing shares lost $5.01, dropping 4.7 percent to $101.87. At its peak, the selling knocked off $7.89 a share, or $6 billion of market value. The stock recovered slightly as speculation about the cause of the fire on the Ethiopian Airlines plane shifted away from the batteries.
The cause of the fire — which broke out more than 8 hours after it had landed in London — remained under investigation. The location of the fire led some experts to surmise it was not the plane’s lithium-ion batteries.
Meanwhile, an unspecified mechanical issue caused another 787 flown by Thomson Airways to return to Manchester Airport, adding to concerns about the plane.
Runways at Heathrow were shut down for nearly an hour as emergency crews put out the fire. No passengers were on the plane.
Boeing’s stock partially rebounded after photos were circulated showing the section of the plane damaged by the fire — an area near the tail, far away from the battery compartment.
‘‘Evidence thus far suggests that the battery was not the cause of the fire at Heathrow,’’ Jason Gursky, an aerospace analyst with Citigroup told investors. ‘‘The images out of London are not consistent with the [battery] fire at Boston Logan, which prompted the grounding earlier this year.’’
The unanswered questions, however, kept the company’s stock sharply lower throughout the afternoon. Friday’s loss ultimately shaved $3.8 billion from Boeing’s market capitalization.
Boeing spokesman Marc Birtel said in an e-mail that the company had personnel on the ground at Heathrow and that the company ‘‘is working to fully understand and address’’ the situation.