Prime Minister Justin Trudeau revealed the plan to ship what he called "heavy artillery" earlier this week, but offered no details on what the Canadian military would be donating.
"Their most recent ask was exactly for that, for heavy artillery, for reasons of operational security," Trudeau said on Wednesday. "I can't go into the details at this point on how and what we're getting to them exactly."
Read more: Britain, US To Train Ukrainians Use Modern Western Armament Including 155mm M777 Howitzers and Armored Vehicles
Three defense sources — who spoke to CBC News on the condition they not be identified because they were not authorized to speak publicly about the file — say four of the 37 howitzers Canada purchased during the Afghan war were earmarked for shipment.
Defence Minister Anita Anand acknowledged the shipment in a media release Friday but did not provide specifics, saying only that "a number of M-777 howitzers" were sent to Ukraine "in conjunction with our American allies."
Later Friday, during an interview on CBC's Power & Politics, Anand said "there are certain details that we are keeping confidential for security reasons."
The big guns come out of the inventory of the 1st Regiment, Royal Canadian Horse Artillery, based in Shilo, Manitoba, said two of the confidential sources.
The shipment included an unspecified amount of ammunition, the statement said.
One of three defense sources said the package included a number of precision-guided Excalibur rounds left over from the Afghan war. The GPS-guided shells are worth about $112,000 US per round.
Canada recently shipped a portion of its aging stock of Carl Gustaf anti-tank weapons to Ukraine and the Department of National Defence said it has provided a "significant number of additional" anti-armour rockets, which were requested by the Ukrainians.
Anand said Canada is also in the process of finalizing contracts for "a number of commercial pattern armoured vehicles, which will be sent to Ukraine as soon as possible." Ottawa also has implemented a service contract for the maintenance and repair of specialized drone cameras Canada has already supplied to Ukraine.
"As Ukrainians fight to defend their sovereignty, freedom, and independence, Canada remains committed to continuing to provide Ukraine with the military equipment that it needs to fight and win this war," Anand said in the media statement.
The M982 Excalibur (previously XM982) is a 155 mm extended range guided artillery shell developed during a collaborative effort between the U.S. Army Research Laboratory (ARL) and the United States Army Armament Research, Development and Engineering Center (ARDEC). The Excalibur was developed and/or manufactured by prime contractor Raytheon Missiles & Defense, BAE Systems AB and other subs and primes in multiple capacities such as Camber Corporation and Huntington Ingalls Industries. It is a GPS- and inertial-guided munition capable of being used in close support situations within 75–150 meters (250–490 ft) of friendly troops or in situations where targets might be prohibitively close to civilians to attack with conventional unguided artillery fire.