Five teenagers have been arrested in connection with a blaze which closed the M1 in both directions, Scotland Yard said.
The youths, aged between 14 and 17, were arrested in a series of raids across Barnet and Harrow in north London on Wednesday morning.
They are being held in connection with the blaze that damaged the motorway bridge directly above a north London scrapyard on April 15, as well as two other fires, said police.
The M1 blaze has been linked to two others in the Moat Mount Open Space in Mill Hill, north London, one between April 14 and 15 and the other between April 15 and 16.
Detective Chief Inspector Mark Roycroft said: "Although we are pursuing a number of active leads into these fires we would still ask that anyone who has any information about these crimes contact Barnet police.
"Your information could be invaluable to the investigation and bringing those responsible to justice."
The fire-damaged section of the M1, between junctions one and four, only fully re-opened six days after the blaze and further closures may be needed in the future so permanent repair work can be carried out.
The damage to the elevated section of the motorway in Mill Hill led to huge delays for football fans and marathon runners travelling to and from the capital.