The 237 meter long, 47121 dwt container vessel MSC Nederland collided with the 245 meter long, 101970 dwt chemical tanker Elka Apollon on the Houston Ship Channel near light 75.  The collision sent three containers off the Nederland onto the deck of the tanker.   One container containing tractor equipment has leaked hydraulic oil onto the deck of the Elka Apollon.  No reports of injuries.  The Coast Guard is conducting an investigation into the incident.