A four-month-old baby is fighting for his life and two people have been arrested on suspicion of assault.
Police were called by staff at a hospital in Greater Manchester over concerns over the baby's 'injuries', a spokesperson said.
A man and woman have been arrested on suspicion of assault in connection, police have confirmed. Both are aged 20.
Greater Manchester Police said on Tuesday they remained in custody for questionning.
The baby boy's condition was described by the force as 'critical'.
The man and woman were both arrested in the Salford area, GMP said.
A spokesman said the baby had been taken to hospital for 'medical assistance'.
No further details have been issued by the police, Manchester Evening News reports.
The man and woman haven't been named.
Police said enquiries were continuing.
In a statement, GMP said: "Shortly before 12.30pm on Sunday, August 9, police were called by hospital staff to concerns over the injuries of a baby boy who had been brought in for medical assistance.
"The four-month-old baby boy remains in a critical condition.
"A man and a woman, both aged 20, were arrested in the Salford area on suspicion of section 18 assault.
"They remain in custody for questioning.
"Enquiries are ongoing."
The force has issued an appeal for anyone with information to come forward.
Call police on 0161 856 3653 or 101 quoting incident number 1761 of 09/08/2020, or Crimestoppers on 0800 555 111.