Here are the latest developments
The car used by the attackers, a Toyota Fortuner, has been found abandoned in a field 6 km away. An AK 47 rifle and two pistols have also been found.
Many people have been held for questioning, say the police. Reports that a woman cop is also being questioned are unconfirmed.
Mr Teotia, 49, was travelling to Ghaziabad in his SUV when the attackers pulled up alongside and opened fire. The gunmen managed to escape.
The politician, hit by six bullets, was taken to a hospital in Noida in a serious condition. Five others were injured.
The police say Mr Teotia had a dispute with a criminal, Rakesh Hasanpuria, who was killed in an encounter. His wife is believed to be the woman constable who has been detained.
"It is very shocking," said Home Minister Rajnath Singh, targeting the UP government. "Law and order is a state subject, ultimately it is their responsibility," he added.
Mr Teotia contested the 2012 Uttar Pradesh Assembly election but lost. He is a prominent member of the BJP's kisan morcha or farmers' body.
He was driving back from Muradnagar, 45 km from Ghaziabad, after a family function when he was attacked.
Hospital officials say Mr Teotia is in a critical condition and a team of doctors is monitoring his treatment.
The attack has taken place at a time political parties have stepped up their campaign for the UP polls next year.
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