A second officer is being investigated for assault following an incident at Manchester Airport, the police inspectorate said.

A video showing a police officer kicking and stamping on the head of 19-year-old Fahir Amaaz while he and his brother Muhammad Amaad, 25, are being detained by police sparked protests in Rochdale and inner Manchester after it was released last month.

Days later, further footage emerged, obtained by the Manchester Evening News, showing the immediate lead-up to the riots on July 23, when two policewomen were knocked to the ground before a taser was used on Mr Amaaz.

In a press conference earlier this week, the family’s lawyer claimed the men’s mother, Shameem Akhtar, 56, was struck in the face with a taser by a police officer.

In the days following the incident, the Independent Office for Police Conduct (IOPC) announced that a Greater Manchester Police (GMP) officer was being investigated for assault in connection with the brothers’ arrest.

In an update on Thursday, the regulator said a second officer had been informed that they were also being investigated for assault. The incident related to an incident shortly afterwards in which two other men were arrested.

The officer is also being investigated for possible gross misconduct due to alleged violations of police professional standards, including the use of force.

An IOPC spokesman said it had received another complaint from GMP containing several detailed allegations from one of the parties involved.

IOPC Regional Director Catherine Bates said: “It is clear that the situation at Manchester Airport was complex and escalated rapidly.

“The incident, which resulted in injuries to both police officers and members of the public, has understandably caused concern and we are working hard to compile all relevant events from that day.

“At the same time, Greater Manchester Police are investigating whether any crimes were committed by citizens during the initial altercation and subsequent arrests.

“These investigations are taking place separately and we are in contact with the public prosecutor’s office to determine how they can continue in parallel.”

The IOPC spokesman said the investigation would examine whether the treatment may have been influenced by discriminatory behaviour.

It examines the use of violence against six citizens in two incidents: the first involves the arrests shown in the footage, and the second, shortly afterwards, in which two more men were arrested and one of them was sprayed with Pava spray.

It is also examining allegations relating to the way in which a woman who said she was injured during the arrests was cared for and to a young child who was present at the time of the arrest. It is also examining allegations relating to the language and level of force used by police towards two of the men arrested and the subsequent detention of the men.

Four men were arrested after the incident on suspicion of affray and assault and later released on bail.

A GMP spokesman said the four remained on bail.

He said: “Our operational team, led by an experienced senior investigating officer, is making good progress in investigating alleged criminal offences against both members of the public and police officers and we are determined to conclude the investigation as quickly as possible in the interests of justice.

“This is a complex case so we ask the public for patience while we ensure the investigation is conducted thoroughly.

“We also remain fully committed to supporting the IOPC-led investigation into the actions of our officers.”