Police have today, Sunday, launched a murder investigation - here's everything we know so far:
* The incident took place in Oakdale Avenue in Peterborough
* Police were called at 7.10am today, Sunday, October 21
* A man in his 20s was found dead in a parked car
* He was taken to Peterborough City Hospital.
* She is currently at Thorpe Wood Police Station in Peterborough.
* Officers have this morning been given an extra 12 hours to question the woman and she remains at Thorpe Wood Police Station in Peterborough.
* She has been released under investigation
* A post-mortem to establish the cause of death took place at Peterborough City Hospital this morning.
*He died from a single stab wound to the chest
* The man, named to the Peterborough Telegraph locally as a 23-year-old man of Eastern European descent, is still to be formally identified.
* Detective Chief Inspector Adam Gallop wants to hear from anyone who saw or heard any disturbance in the Oakdale Avenue area between 5am and 7am on Sunday.
* Anyone with information should call police on 101 quoting incident number 93 of 21 October or visit www.cambs.police.uk/report
* Alternatively, contact Crimestoppers, anonymously, on 0800 555111 or via www.crimestoppers-uk.org