A fifth person has been arrested in connection with a serious crash in the Manorway, Corringham which left a woman needing to have part of her leg amputated.
Two motorbikes were in collision at around 9.15pm on Wednesday, June 14.
One of the riders, a woman in her 20s, suffered serious injuries.
A 26 year-old man from Romford was arrested on Sunday, June 25 on suspicion of assisting an offender.
He has been released under investigation.
Four other people have already been arrested on suspicion of assisting an offender and all have been released under investigation.
Sergeant Peter Swan, from the Serious Collision Investigation Unit, said: “We are making good progress with this investigation but are still appealing for anyone who has information about the crash who we’ve not spoken with to come forward.
“We still want to speak to the rider of the offending motorbike and investigations are continuing to locate them.
“If anyone has any information about their identity or where they are, I would urge them to contact us.
“A woman has suffered a serious life changing injury and it is important we bring all those responsible to justice.”
Anyone with any information is asked to contact the Serious Collision Investigation Unit on 101 or via email: email@example.com or Crimestoppers anonymously on 0800 555 111.