Columbia Pipeline Group Inc. opened an offer to exchange about $2.7 million in outstanding unregistered senior unsecured notes, the company said April 14.

Unregistered 2.45% notes due 2018, 3.30% notes due 2020, 4.50% notes due 2025 and 5.80% notes due 2045 will be exchanged for the same amount of registered notes.

The exchange offer will expire on May 12, the company said.