LONDON (Reuters) - The investigation into a nerve agent attack on former Russian double agent Sergei Skripal and his daughter is likely to take several months as it is one of the most complex undertaken by British counter terrorism officers, police said on Monday.

“This is one of the largest and most complex investigations undertaken by British counter terrorism policing,” the Metropolitan Police said in a statement. British counter terrorism police were involved in investigating five major attacks last year.

“The investigation is highly likely to take many months,” the statement said.