FACTBOX: Facts about Mumbai attack suspects in India

(Reuters) - Indian police forged ahead on Sunday with their investigation into the Mumbai attacks which killed 171 people last week. Four men are in custody, only one of them from Pakistan, which is where India says the attack originated.

Here are some facts about the suspects and the roles they are accused of playing:

MOHAMED AJMAL KASAB: For India, the 21-year-old is the smoking gun proving a Pakistani hand in the attacks. Kasab is the only survivor of the 10 gunmen who attacked Mumbai sites

last week, and is the prime source for Indian investigators. Captured wearing a t-shirt emblazoned with the Versace designer label outside the main train station in Mumbai, the baby-faced gunman, and an accomplice who was shot dead, had fired AK-47s inside and killed around 50 people. He told investigators he comes from Faridkot in Pakistan's Punjab region. Recruited by the Laskhar-e-Taiba (LeT) militant group, he was given a year of commando training in Pakistan by a former Pakistani military officer, he told interrogators. LeT is on U.S. and Indian terrorist lists, and Kasab told police the gunmen took orders by phone from two LeT operations chiefs. One, Zaki-ur-Rehman Lakhvi, was designated a terrorist by the United States in May. India says the other, Yusuf Muzammil, is the head of LeT's anti-India operations. Police had identified their captive by other aliases including Azav Amir Kasav, but have officially identified him as Mohammed Ajmal Kasab. Kasab is the Urdu word for butcher, which police say was his father's profession. They say it is not clear whether it is his real name.

TAUSIF RAHMAN: Police arrested the clerk from the eastern Indian city of Kolkata after tracing back to him the mobile phone cards used by the attackers. Rehman used a dead relative's identity documents to acquire the 22 mobile phone cards, which he later sold to Mukhtar Ahmed. He has been charged with conspiracy and forgery. He was arrested after Kasab and police say he helped them catch Ahmed, who was in New Delhi.

MUKHTAR AHMED: A native of Indian Kashmir, arrested on Friday. Soon after his arrest, Kashmir police said he had been their informant in an informal anti-militant network for years and had recently been hired formally as constable, a low-ranking job. They were investigating whether he may have been on undercover duty when he passed the mobile phone cards to the attackers. Police have not said how he did that. He had worked as a street vendor and three-wheel-taxi driver in Kolkata for a time. He started helping police after his brother was killed by Muslim militants in Kashmir, Kashmir police said.

FAIM ANSARI: The 26-year-old Mumbai native has been in jail in the north Indian state of Uttar Pradesh since February, when he was arrested carrying maps with a number of Mumbai landmarks highlighted, several of which were attacked last week. Police say he told them he was trained by LeT after being recruited in Dubai, and almost certainly reconnoitred Mumbai during the planning of the assault. Sometime before February, he returned from Pakistan to India with the assumed name of Sahil Pawaskar, which he used to enrol in a computer school in Mumbai. He rented an apartment near the stock exchange building, which was marked on his maps and may have been a target. Uttar Pradesh police said Mumbai police returned him to them long ago and only now are coming to question him. The facts of his arrest only emerged last week, and were the first sign of Indian complicity.