Following a massive protest by local residents, clerics and seminary students, police arrested Dr Iftikhar A Khan, who was accused by his nephew of having committed blasphemy.
"The content recovered from the suspect's possession appears to be blasphemous. However, we still need to determine its context," The Express Tribune quoted a senior police official, as saying.
The officer added that it is up to the court to decide whether the accused is guilty of blasphemy. If proven guilty, he could be sentenced to life imprisonment or even death.
Dr Khan will be produced before a court on Monday to obtain his physical remand for further investigation, the official added.
Police said the complainant, Sheikh Usman, would also be questioned as to why he took 11 years to report the alleged blasphemy - the text in question had been written in 2001.
"Dr Khan had filed a Rs5 billion damages claim against Usman in some civil case. This could be the reason why the latter reported the case just now," another police official said.
The official said Usman's father Sheikh Rashayad had told the police that his brother started using language which could be interpreted as blasphemous, several years ago. He claimed his family had not been on speaking terms with Dr Khan for the past five years. Rashayad maintained his family never mentioned his brother's work out of fear for their own lives.
However, the question remains as to why Usman chose this moment to report Dr Khan's act, the paper said.
Police said that Dr Khan has so far rejected the allegations against him. He said that his book, which allegedly contains blasphemous passages, was an unpublished personal draft. The copy of the confiscated book, however, shows that it was published in 2001 and that at least 1,000 copies were distributed, he added. (ANI)