The following summarizes the components of current portion of real estate properties under development as at December 31, 2019 and 2020:

At December 31,	2019		2020
	(’000)		(’000)
Construction in progress		—		9,636
Land use right		—		112,057
Net book value	$	—	$	121,693

The following summarizes the components of non-current portion of real estate properties under development at December 31, 2019 and 2020:

At December 31,	2019			2020
	(’000)			(’000)
Building at cost	$	27,732		$	31,678
Less: accumulated depreciation		(15,007	)		(16,065	)
		12,725			15,613
Construction in progress		156,221			92,533
Land use right		82,739			82,346
Net book value	$	251,685		$	190,492

Real estate properties under development of $147.5 million (2019: $81.7 million) have been pledged to banks to obtain loan facilities (See Note 9).

Included in construction in progress were capitalized debt issuance costs and interest for bank loans amounting to $1,754 (2019: $1,473) and $10,866 (2019: $707), respectively.

The Company leased its buildings to third parties with the carrying amount as shown below:

At December 31,	2019			2020
	(’000)			(’000)
Buildings at cost	$	27,732		$	31,678
Less: accumulated depreciation		(15,007	)		(16,065	)
Buildings, net	$	12,725		$	15,613

In 2020, a total of $53.7 million was transferred to real estate properties held for sales type lease from real estate properties under development, and by the end of 2020, a total of $23.7 million was recognized as cost of sales due to the delivery of Towers 2, 8 and 9 of Nam Tai Inno Park. Real estate properties held for sales type lease of $29.4 million (2019: Nil) have been pledged to banks to obtain loan facilities (See Note 9).

In 2020, a total of $92.8 million (see Note 5) was transferred to real estate properties held for lease from real estate properties under development.