Police in India's southern state of Andhra Pradesh have detained at least six people in connection with an attempt to assassinate the chief minister.
Chandrababu Naidu narrowly escaped with his life when landmines went off near his car on Wednesday.
Four others were more seriously hurt in the incident.
Naidu fractured his collar bone, but is now back home
Police accuse the six detainees of helping suspected Maoist rebels to carry out the mine attack.
Commandos of India's elite National Security Guards have launched an inquiry into the incident.
The state government has also asked a former police officer to investigate the security breach.
S Subramaniam, who founded the elite Special Protection Group which protects the Indian prime minister and family, will try to determine whether there were any lapses in Mr Naidu's security arrangements.
Naidu back home
Police suspect the outlawed People's War Group (PWG) was behind the attack.
"Though there are no claims so far, the nature of the attack and the use of Claymore mines point a finger at the PWG," state police chief SR Sukumara told the AFP news agency.
"The probe will not spare either the culprits or security officials."
He has denied that his men failed to check Mr Naidu's route thoroughly.
Mr Naidu was travelling on a forest road between the Hindu temple sites at Tirupati and Tirumala when the mines were detonated - triggered by a flash camera, police say.
The bullet-proof Ambassador car carrying the chief minister was completely destroyed.
Claymore mines carry a small charge packed behind hundreds of steel balls. On detonation, the balls shoot forwards and are likely to kill anyone in their path.
Mr Naidu fractured his right collar bone and sustained injuries to his left leg.
He is now back in his residence in the state capital, after receiving treatment in a local hospital.
State cabinet minister B Gopala Krishna Reddy, two state legislators from Mr Naidu's Telegu Desam Party (TDP) and his driver also survived the attack.
Mr Naidu is one of the political leaders on the hit list of the PWG, which has waged a 30-year insurgency on behalf of landless farmers in which thousands have died.
He is a key ally of Indian Prime Minister Atal Behari Vajpayee and is often named as a potential national leader.
The PWG has carried out such blasts in the past, targeting politicians and police officials.
The former home minister of Andhra Pradesh, A Madhav Reddy, was killed in a massive landmine blast in March 2000 at Ghatkesar near Hyderabad.
Activists of Mr Naidu's party took to the streets on Wednesday of Tirupati, smashing windscreens of buses in protest at the assassination attempt.
More demonstrations were held across the state on Thursday.
"It is shocking that the PWG got so close to the chief minister.
The police know that he is on the PWG hit list. They should have
taken more precautions," said R Chandrashekhar Reddy, a TDP leader.