* Analysts had expected a 0.3 percent increase
* Lower sales of petroleum, coal and primary metals to blame
* Some refineries reported slowdowns longer than usual
* Inventories reach record high
OTTAWA, June 14 (Reuters) - Canadian factory sales unexpectedly fell by 2.4 percent in April from March, dragged down in part by lower sales of petroleum products due to refinery slowdowns, Statistics Canada data indicated on Friday.
Analysts had expected a 0.3 percent increase. The drop is the fourth in five months and the biggest retreat since the 2.5 percent fall recorded in August 2009.
Sales were down in 13 of 21 industries, representing about 86 percent of Canadian manufacturing. Constant dollar sales fell by 1.6 percent on lower sales volumes.
Petroleum and coal product sales plummeted 8.8 percent in April and are down 14.0 percent since November 2012. Petroleum refineries account for 93 percent of sales in the petroleum and coal product category.
"In April, some refineries reported that either maintenance or the switch to summer fuels required production to be slowed or halted for a longer than normal period of time," Statscan said in its daily commentary.
Inventories rose by 0.6 percent - the fourth consecutive monthly increase - to a record high. The inventory-to-sales ratio rose to 1.43 in April from 1.39 in March, matching the 1.43 recorded in October 2009.
Graphic - Canadian manufacturing sales: