A 17-year-old boy was rushed to hospital after he was stabbed in a street brawl in south London.
Police raced to the scene after reports of a fight between a "large group" of youths outside the Tesco on Streatham High Road.
The area was cordoned off and police arrested another boy, 16, following the fight.
Police believe it was a stabbing and said a knife was recovered from the scene.
Officers said they were called at 1.50pm on Saturday to reports of an altercation on the busy south London road.
At just after 9.30pm on Saturday, police told the Standard the wounded teenager's injuries were not believed to be life-threatening.
A spokesman for the Met Police said two buses which are being kept within the police cordon are not involved but could hold key witnesses who could help in shedding light on what happened.
Witnesses told the Standard they saw a knife which had been bagged by police.
A police helicopter was also reported to have been circling overhead.
Officers have asked Tesco for CCTV footage facing out into the road, one witness said.
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