Detectives are linking two separate sexual assaults on teenage girls who were on their way to school in Burnley, Lancashire.
A 14-year-old girl had her skirt pulled down by a man as she walked along Leyland Road on Tuesday at 0900 BST.
And a 13-year-old girl had her clothes pulled by a man as she walked along the same road at 0830 BST on Thursday.
Police said both girls, who were wearing their school uniforms, were left "very distressed" by the attacks.
Det Insp Simon Cheyte said: "Due to the similarities of the two offences we do believe they could be linked.
"Leyland Road is a busy road and there will have been a good number of people around at those times of the morning so I would urge people to think back and contact us if they have seen anything suspicious.
"These incidents, I know, were very distressing for both the young girls involved and we are extremely keen to trace this individual as soon as possible."
The man in the first attack was described as white, in his 30s and about 5ft 10ins tall, wearing a black hooded top and dark jeans.
The attacker in the second assault was given a similar description except that his victim said he was in his 20s.