COLUMBIA, S.C. (AP) — Aiken County deputies and state agents quickly protected a number of sites across the county after a January train wreck in Graniteville just in case the collision and deadly chlorine gas spill was an act of terrorism.

It turned out the wreck was caused by human error, according to investigators. But in a report released Monday, the sheriff’s office gave itself mostly high marks for the quick response in the hours after the crash and keeping the site secure and the return of evacuees orderly in the days after the crash.

The 11-page review of how the sheriff’s office handled the Jan. 6 crash details both what was done right and what can be improved.

‘‘This document will be invaluable in preparing for future incidents,’’ Sheriff Michael Hunt said.

The crash happened when a train heading through the town around 2:45 a.m. barreled on to a side track and smashed into several parked railcars. A tanker car carrying chlorine ruptured, causing a dense and highly toxic cloud of the gas to spread through the mill town. Federal investigators say the crew of the parked train failed to flip a switch.

The Graniteville crash killed nine people and injured 250 more. It was the deadliest train wreck involving hazardous material in nearly three decades.

Authorities evacuated homes and businesses within a mile of the crash, affecting about 5,400 people. Some were out of their homes for more than a week.

The sheriff’s report praised the rapid response, aided by gas masks and other equipment officers carried in their cars. The response was safe too. Occupational Safety and Health Administration officials found no concerns when they arrived a day after the wreck.

The report said deputies did a good job getting news out about the wreck and setting up a safety perimeter around the crash.

But the sheriff’s office said a reverse 911 system that calls homes in an area and gives a recorded message was not activated quickly enough because only emergency management employees could access the system. Otherwise, communication during the crash and the aftermath went well. Local, state and federal officers followed established plans to secure a number of sites across Aiken County in case the wreck was caused by a terrorist. New radio systems allowed a number of different agencies to communicate easily, according to the report.

The sheriff’s office reported few major problems. In the hours after the crash, the coroner did not have protective equipment to get close to the wreck.

Officials hope money from homeland security can solve that problem.