SB 10.45.41

The ocean said, "I have not taken the boy. The daitya named Pancajana has taken the boy. He is a powerful demon whom I cannot defeat." The last part of verse forty and the first part of verse forty one are one sentence. There is also an additional line added according to Vaisnava tosani (aste tenahrto nunam tac chrutva satvaram prabhuh).Prabhu becomes the subject of the next line. Taking the conch shell, he mounted his chariot which he had left on the shore of the ocean. Though Krsna is omniscient, and knew that the boy was not in the ocean, he left Balarama on the shore along with the chariot, and went into the ocean with the pretext of searching for the boy to obtain his own conch shell. The conch shell was a product of the body of the asura panca jana (tad anga prabhavam). But because the conch was spiritual, it was also eternal. Like Jaya and Vijaya the conch had temporarily attained the qualities of a powerful asura according to some explanations. The Avantai Khanda of the Skanda Purana says "Having killed Pancajana, the great asura in the form of an aquatic, Krsna took the conch which had been swallowed by him previously (tan madhya stham)." From this evidence some people explain that the conch was residing within the demon’s body (and merely came out of the demon’s body (tad anga jatam) when Krsna killed him .