A second teenager has been arrested in connection with an incident in which noxious liquid was thrown at four men in Grays.
An 18-year-old man has been arrested on suspicion of causing grievous bodily harm and is in custody for questioning.
A 17-year-old boy who was previously arrested on suspicion of causing grievous bodily harm also remains in custody for questioning.
ESSEX Police are investigating an incident in which four people were attacked with an unknown substance in Chafford Hundred.
A spokesperson said: “We were called shortly before 8.10pm on Monday 25 February with reports four men had been assaulted by a group of men on a footbridge linking Chafford Hundred train station and intu Lakeside shopping centre.
“They have been taken to hospital with facial injuries, which are not believed to be life changing or life threatening.
“A 17-year-old boy was arrested on suspicion of causing grievous bodily harm. He has also been taken to hospital as a precaution.
Enquiries are ongoing to find two other people believed to have been involved in the disturbance.
“We are aware there were witnesses at the scene who filmed the incident and we ask them and anyone with information to call Grays CID on 101 quoting incident 1136 of February 25.
“Alternatively, contact the Crimestoppers charity 100% anonymously on 0800 555 111 or use the anonymous online form at Crimestoppers-uk.org.”