Paris attacks: French officials seek second fugitive involved in assault on capital, while Hannover on alert after 'concrete security threat'

French officials have revealed they are seeking a second fugitive involved in the deadly attacks carried out in Paris last week, as a bomb threat caused chaos in the German city of Hannover.

Three French officials who spoke to the Associated Press on condition of anonymity have said an analysis of the attacks in the capital on 13 November that killed 129 people indicated that one person directly involved in the assault has been unaccounted for.

The person has not been identified, and is said to be sought in addition to Salah Abdeslam, 26, a Belgian-based Frenchman, who is on the run and is wanted on an international arrest warrant.

Witnesses suggested a third man had been in a black Seat with Salah Abdeslam and his brother Ibrahim as they drove around the French capital, engaging in machine gun attacks. The BBC reported that French security sources believe a ninth assailant was involved in the attacks after a surveillance video possibly revealed a third figure riding in the car.

Meanwhile, a "concrete security threat" caused police to evacuate Hannover stadium in Germany less than two hours before an international football match between Germany and the Netherlands was due to start.

No explosives were found at the stadium, but two further sites - a music venue and a train station - were evacuated. A bomb disposal unit later removed a suspicious package from a train at the city's station. The hunt is now on for the man who left the package and the two Paris suspects as the search spread further across Europe.

Seven attackers died on the night of 13 November — three around the national stadium, three inside the Bataclan concert venue, and one at a restaurant nearby. A team of gunmen also opened fire at a series of nightspots in one of Paris' trendiest neighbourhoods.

A justice official told Reuters: "We are in the process of determining how many there may have been. Nothing is ruled out. There's a very strong theory that there was one more, but there may have been even more."

French police have also issued a photo of one of the suicide bombers who targeted the Stade de France last week, asking for information from anyone who recognises him.

Ibrahim, 31, blew himself up on the Boulevard Voltaire and Salah is now the object of a Europe-wide manhunt.

The development came as Belgian police said two suspects charged after a wave of arrests in Brussels could have been the bomb-makers behind the Paris attacks. Police reportedly found bomb-making ingredients including ammonium nitrate and fertiliser as well as bullets at the homes of Hamza Attou, 21, and Mohammed Amri, 27. Both have been charged with terrorist acts and being part of a terrorist conspiracy but denied the fertiliser was to make explosives.

The men’s lawyers say the pair admitted driving from Brussels to Paris early on Saturday to pick up Abdeslam. It was claimed Abdeslam called Amri to say his car had broken down, offering to pay for the petrol and road tolls. The lawyers insisted neither man knew Abdeslam was suspected as being part of the Isis death squad.

Abdeslam was also revealed to have travelled to Austria from Germany in September, the Austrian Interior Minister Johanna Mikl-Leitner told ORF radio.

Additional reporting by agencies