Four teenagers have been arrested in north London on suspicion of being involved in acid attacks.
They were detained on the Andover Estate in Islington in the early hours of the morning having been tracked by a police helicopter.
Police said they had dumped a stolen moped and other items before entering an address where they were arrested.
Officers said they were not detained in connection with a specific incident.
The number of attacks involving corrosive fluids has risen sharply in the capital in recent years.
There were 454 such crimes last year compared to 261 in 2015.
The four teenagers were "not detained on the basis of information connecting them to a specific acid attack", officers said.