Seven police officers have been injured after being sprayed with a corrosive substance.
Lancashire Police said they was attacked while responding to an emergency call in Darwen, with the suspect jumping out of a first-floor window.
“A number of officers had forced entry to an address on Ash Grove in Darwen following a call reporting a domestic incident, when they were sprayed with what is believed to be an ammonia cleaning liquid,” a spokesperson added.
“The offender escaped through a first-floor window but was arrested a short time later.”
Seven officers were taken by colleagues to the Royal Blackburn Hospital and six have been discharged.
One, a sergeant, suffered serious damage to his eyes, throat and respiratory system and remains in hospital.
Supt Andrea Barrow said: “This shocking incident from the early hours of the morning has left an officer with some significant and serious injuries. My thoughts are with him and his family and I wish him a speedy recovery and look forward to his return to work.”
Andy Rhodes, the chief constable of Lancashire Police, said the incident showed “the dangers that officers face and how they put their lives on the line each and every day to protect people”.
A 46-year old man from Darwen is currently being held on suspicion of Section 18 wounding and police enquiries continue.
Ammonia has been used as part of a trend of corrosive substance attacks across the UK.
It was poured down a man's throat in one brutal attack over a music video in London last year.
The victim was put in an induced coma and the attackers were jailed.
Members of the public and police officers were injured when ammonia was launched during a fight between rival gangs outside a Northampton McDonalds in 2017.
Three men have since been jailed for their part in what police called a "horrendous, indiscriminate attack".
